1. Field of the Invention
The instant disclosure relates to an optical structure; in particular, to a liquid crystal lens structure and a driving method thereof.
2. Description of Related Art
The liquid crystal lens structure is a lens capable of varying focal length. When the liquid crystal lens structure is in use, an external circuit applies a voltage signal to electrode layers to generate an electrical field between the electrode layers that are arranged on two sides of a crystal liquid layer. The deflection angle of the liquid crystal molecules in the liquid crystal layer is controlled by the electrical field in an orderly fashion in order to provide optical effects similar to an optical lens. When light rays pass through the liquid crystal lens structure, paths of the light rays are affected by the orientation of the liquid crystal molecules to provide optical effects of focusing and defocusing.
Typically, the arrangement of liquid crystal molecules in the liquid crystal lens structure provides optical lens effects by modifying the structural design of the electrodes. Please refer to FIGS. 1A to 1C. As shown in FIG. 1A, a conventional liquid crystal lens structure includes a liquid crystal layer 110, a first substrate 102, a second substrate 104, a first transparent conductive layer 106 located between the liquid crystal layer 110 and the first substrate 102, and a second transparent conductive layer 108 located between the liquid crystal layer 110 and the second substrate 104. The first substrate 102 and second substrate 104 are arranged on opposite sides of the liquid crystal layer 110, or the liquid crystal layer 110 is interposed between the two substrates. FIG. 1B shows a top view of the first transparent conductive layer while FIG. 1C shows a top view of the second transparent conductive layer of the conventional liquid crystal lens structure. The first transparent conductive layer 106 is a structural layer without any openings, whereas the second transparent conductive layer 108 has a circular opening 112.
The second transparent conductive layer 108 includes a circular opening 112 in order to generate a progressive electrical field that applies on the liquid crystal layer 110, so that the angle and refractive index distribution of the liquid crystal molecules resemble that of a quadratic curve distribution, which provides the characteristics of optical focusing. However, since each liquid crystal molecule in the circular opening 112 does not receive the same amount of voltage, the timing for each liquid crystal molecule from the beginning of the rotation to the targeted deflection angle varies, which can affect the overall response time. Notably, the liquid crystal molecules located at the center of the circular opening 112 rotate at a relatively slower rate. The inventor identified that the transparent conductive layers 106 and 108 that are located on two sides of the liquid crystal layer 110 for electrodes and the electrode design of the second transparent conductive layer 108 that has a circular opening 112 cannot possibly provide short enough response time. In order to reduce the response time with limited voltage, redesign and new arrangement of the electrode structure in a liquid crystal lens structure is necessary to enhance performance.
To address the above issues, the inventor strives via associated experience and research to present the instant disclosure, which can effectively improve the limitation described above.